With the remastered and expanded edition of his 1989 Flowers in the Dirt album less than a month away, Paul McCartney has posted one of the set's bonus tracks — the original demo of the LP's first single "My Brave Face," one of several songs written with Elvis Costello.

McCartney looked back on the genesis of his collaboration with Costello in a retrospective post at his official site, recalling that the two were hooked up by McCartney's manager at a time when he was "looking for someone to work with, trying to think of something imaginative to do."

The duo ended up face-to-face in the studio with their guitars, a songwriting setup that hearkened back to his days with John Lennon. "I had said to him early on that this is how I’d written with John, with me being left handed and him being right handed, it was almost like looking in a mirror," wrote McCartney. "We did virtually what John and I did, which was just make up a song a day."

Working in such close proximity also allowed McCartney and Costello to get their demos tracked quickly — and end up with recordings that captured the songs in the glow of that first fresh spark of creativity. All these years later, McCartney still thinks they sound special.

"Because we were working above the studio, we’d just go downstairs and make the record, just the two of us singing exactly what we had made up," he continued. "So there were a few recordings that haven’t been released. We keep saying to each other that they’re good because they are raw, it’s hot off the skillet."

Flowers in the Dirt is scheduled to continue McCartney's ongoing Archive Collection on March 24, when it's set to arrive in stores in an array of deluxe configurations that offer everything from previously unreleased recordings to a hardcover book commemorating the sessions. Check out the full details.